http://hackage.haskell.org/trac/ghc/ticket/4277 Proposal: Significant performance improvements for Data.Map Description Milan Straka's recent [52] Haskell Symposium paper (PDF) shed light on the containers:Data.Map library, indicating there were both algorithmic and stylistic performance improvements to be made. 52. http://research.microsoft.com/~simonpj/papers/containers/containers.pdf This proposal provides a patch that [53] dramatically improves performance across the API. Three standard techniques are applied to the code: * [54] Worker/Wrapper transformations of recursive functions with constant arguments (aka. the [55] static argument transformation). * Explicit inlining of wrapper functions. * Explicit strictness of keys to functions. 53. http://is.gd/eJHIE 54. http://www.workerwrapper.com/ 55. http://hackage.haskell.org/trac/ghc/ticket/888 Three complementary, but orthogonal patches are provided. 1. Add a testsuite, [56] with coverage data (currently 91% of top level functions, and all core functions). 2. Add a micro-benchmark suite based on [57] Criterion, for empirical evidence of improvements to each function. 3. The optimization patch itself. All 3 patches should be applied, under this proposal. 56. http://code.haskell.org/~dons/tests/containers/hpc_index.html 57. http://hackage.haskell.org/package/criterion The [58] benchmark results are very strong: * An average speedup across the core api of 47% (on intel i7 / linux 64 bit), and; * 36% on Mac / intel core 2 duo 32 bit). http://i.imgur.com/05BWe.png 58. http://is.gd/eJHIE No bugs were identified in the development of the comprehensive testsuite, which includes a large set of unit tests from [60] Kazu Yamamoto 60. http://twitter.com/kazu_yamamoto/status/22351727559 A fork of the containers package, with the 3 patches (and a version bump to make it easier to test out) is available: darcs get http://code.haskell.org/~dons/code/containers/ Separately, the patches are attached to this ticket. The consideration period is 3 weeks (before ICFP). __________________________________________________________________ Work carried out over 28/29th August, 2010 in Utrecht, NL, by Johan Tibell and Don Stewart.